1. Field of the Invention
The present invention relates to a stereoscopic image-taking lens apparatus attached to a image-taking apparatus which enables exchange of lenses for image-taking parallax images which can be observed in stereoscopic vision, a stereoscopic image-taking system and an image-taking apparatus.
2. Description of the Related Art
A stereoscopic image-taking apparatus for performing stereoscopic vision image-taking of a so-called field sequential method has right and left optical paths, and shutters such as liquid crystal shutters or the like provided in these optical paths, so that right and left parallax images are taken by an image-pickup element by alternately changing a transparent state and a nontransparent state of the shutters. The parallax images which are taken in this manner can be observed by the observer as a stereoscopic image by using a special observing apparatus.
FIG. 8 shows a structure of a stereoscopic image-taking apparatus of the field sequential method. In this figure, reference numeral 801 denotes a focus lens for performing a focus adjustment which is driven by a focus drive circuit 816. Reference numeral 802 denotes a zoom lens for performing a magnification operation which is driven by a zoom drive circuit 817. Reference numeral 803 denotes a correcting lens for a temperature focus correction and a flange back adjustment, which is driven by the correction drive circuit 818.
Reference numerals 804 and 805 denote right and left object mirrors which can be rotated so as to adjust the direction (vergence) of the right and left optical axes. Reference numerals 806 and 807 denote right and left first lens units, and reference numerals 808 and 809 denote right and left shutters. The shutters 808 and 809 are driven by a shutter drive circuit 820 and repeat the opening and closing operation (a transparent state and a nontransparent state in the liquid crystal shutters) alternately at an appropriate period.
Reference numeral 810 denotes a prism which composes optical axes of the light fluxes which are incident through the first lens units 806 and 807, and shutters 808 and 809, respectively, from the right and left object mirrors 804 and 805. As a consequence, the light flux incident from the right and left object mirrors 804 and 805 alternately forms an image on a common image-pickup surface.
Reference numeral 811 denotes an IRIS for making an aperture adjustment and the IRIS 811 is driven with an IRIS drive circuit 815. Reference numeral 812 denotes a second lens unit.
Reference numerals 813 and 814 denote encoders which detect the positions of the focus lens 801 and the zoom lens 802 respectively.
Reference numeral 819 denotes a rangefinding circuit for detecting the distance to an object. This detection signal is sent to the microcomputer 825 which will be described later, and the microcomputer 825 rotates the object mirrors 804 and 805 in accordance with the distance to the object so as to adjust the vergence.
Reference numeral 821 denotes an image-pickup element such as a CCD or the like arranged on the image-pickup surface, and the image-pickup element 821 is driven with the CCD drive circuit 822. Reference numeral 823 denotes an amplifying circuit for amplifying the image signal which is an output of the image-pickup element 821.
Reference numeral 824 denotes a signal processing circuit for processing a signal for white balance, AF, AE or the like and for producing a video signal. Reference numeral 825 denotes a microcomputer which carries out control of the whole apparatus such as the shutters 808 and 809, drive circuits 815 to 817, a signal processing circuit 824 or the like.
This stereoscopic image-taking apparatus is prepared only for the purpose of performing the stereoscopic image-taking. The apparatus is configured in such a manner that a stereoscopic image can be taken with a signal processing system and an apparatus control system (the microcomputer 825) that are exclusively dedicated to the stereoscopic image-taking.
Furthermore, in recent years, a stereoscopic (3D) image-taking lens having a image-taking optical system ranging from the right and left object mirrors 804 and 805 to the correcting lens 803 as shown in FIG. 8, and being attachable to a camera for performing a general 2D image-taking has been proposed.
However, in the case where a 3D image-taking lens is attached to a camera for performing the 2D image-taking, various disadvantages arise.
For example, in some cameras, a so-called slow shutter mode (a mode in which the charge storage time of the image-pickup element is set to, for example, 1/30 of a second or 1/15 of a second which is slower than 1/60 of a second which is regulated by the NTSC method) can be selected. In the case where the 3D image-taking lens is attached to be used with such a camera, the right and left parallax images are taken as a mixed image without being separated from each other, so that an appropriate stereoscopic image cannot be obtained.
Furthermore, since a color difference resulting from an optical error of the right and left object optical paths (for example, a slight color difference of the right and left shutters) and a deviation of images resulting from a parallax are present on images which are formed on the image-pickup element by the right and left optical paths, there is a possibility that white extraction cannot be appropriately carried out by the same method as at the time of 2D image-taking in the case where the white balance setting control is performed on the basis of the image signal of the image formed with these right and left object optical paths.